"Once upon a long ago" I started to contribute to KDE (my longtime DE of choice) for very personal reasons (needed to see my significant-other-at-that-time via IM, who was enduring a life threatening illness, and I refused to use closed source software to do so - but it seems to be a matter to a PBK interview, not a blog).
Despite of our fate as a couple, the fruit of my love for her and for the Free Software ideals was my code, and it was being used by thousands of people. "Why not put my participation in the Free Software Community in my CV?" I did, and things started to fare better as time passed. I was better received in interviews and got some nicer job offerings, even outside Brazil. My local colleagues started to see some sort of übergeek aura surrounding me :), even if I was unwilling or unable to write a simple "hello word" in Delphi (writing a Bluetooth driver or a stream server for Linux is way easier in my opinion). And when I'm asked about what people can do to become Free Software developers, I say the basic statements (use and get used to Free Software, learn how to speak English, identify something that's missing and try to fix/implement/improve it, interact with other developers, etc.).
Being a KDE developer helped me to take care of personal affairs,help other people to communicate using Kopete and to improve my professional life. It's a fine everybody-wins situation, and future contributors should be informed that it will probably be the same to them. ;)